In process control systems, valves and other process control devices have actuators that may be controlled by liquid level detectors, pressure switches, flow switches, and/or other process variable switches. In some examples, the switches have two states (e.g., on/off, open/close, etc.) and are calibrated to cause the switches to switch between the states in response to an associated sensor or detector determining that an associated condition is true or false. For example, a liquid level detector may be calibrated to cause a switch to enter an on state when a liquid level in a vessel or container increases above (or decreases below) a threshold level.